2-Phenyl-as-triazine-3,5(2H,4H)-diones and their use for controlling coccidiosis have been described in U.S. Pat. No. 3,912,723. The phenyl moiety in the said triazines may, inter alia, be substituted with a benzoyl-, an .alpha.-hydroxy-phenylmethyl- and a phenylsulfonyl radical.
Substituted 2-phenyl-hexahydro-1,2,4-triazine-3,5-diones and their use for combatting Protozoa have been disclosed in Published Eur. patent application No. 0,154,885.
The 5,6-dihydro-2-phenyl-1,2,4-triazine-3,5(2H,4H)-diones, described in the present application, differ from the hereinabove-mentioned triazinones, by the specific substitution of the 2-phenyl moiety, resulting in 5,6-dihydro-1,2,4-triazine-3,5(2H,4H)-diones which are very effective in destroying or preventing the growth of Protozoa in subjects suffering from such Protozoa.